Virtual reality force emulation

ABSTRACT

Multi-dimensional, non-linked method and apparatus for producing a simulated feeling of force on a preselected location on a human operator in a synthesized environment accomplished by generating a first, constant, stationary electromagnetic field and a second, varying electromagnetic field local to the human operator. The variance of the second electromagnetic field is controlled by electrical currents which are responsive to parameters describing the position and orientation of said preselected location on the human operator and such variance results in attraction and repulsion of the first and second electromagnetic fields emulating a feeling of force on the human subject.

RIGHTS OF THE GOVERNMENT

The invention described herein may be manufactured and used by or forthe Government of the United States for all governmental purposeswithout the payment of any royalty.

BACKGROUND OF THE INVENTION

This invention relates to the field of generating forces in a virtualreality setting and more specifically to the field of generating forcesin a virtual reality setting without physical attachment to a referencesource.

Virtual reality simulators are widely used for training in space,aviation and large vehicle driving operations where a specificenvironment is simulated so the trainee can learn and practiceappropriate responses. The more realistic the simulated environment, themore realistic the responses learned by the trainee so the trainee'sperformance during a real-time operation is superior. Training invirtual reality simulators is more practical and less costly than usingreal-time operational equipment. Virtual reality simulators simulating avariety of environments are also widely used for recreational purposes.

To make the simulated environment as realistic as possible, there isinterest in producing a feeling of force or proprioceptive feedback tothe human operator as he tries to interact in the virtual environment.In most operational environments, where an operator receives a feelingof force on one or more parts of the body, there is no connection orattachment from the part of the body receiving the feeling of force toany other objects. Most virtual reality systems simulating force,however, must attach or link the part of the body receiving the force toa reference frame and the feeling of attachment minimizes the realism ofthe simulation.

Known systems operate under an action-reaction scenario based on thetraditional Newton's third law concept of bodies in contact in which theequipment attached to the human subject is also attached to either aspring or other force reflecting coupling system or possibly to a trackwhere its motion can be carefully controlled. Attaching a human subjectto a spring or other force reflecting coupling system minimizes theeffectiveness of the simulator when such attachment or coupling does notoccur in an operational environment. When an attached or tethered forcereflecting device is used in today's modem virtual reality simulationsystems, there is a loss of realism as the human becomes aware of histethering to a local stationary frame.

It is known to have force reflection in virtual reality systems inmultiple, as opposed to single dimensions, thus, producing a morerealistic force feeling. However, all known systems in the art arearranged so that a tether, ground source or reference frame is attachedto the human subject.

One goal of the invention is to capitalize on the concept of an “actionat a distance” method of reflecting forces as opposed to the traditionalNewton's third law concept of “action-reaction” with bodies in contactas is used in devices known in the art. The “action at a distance”concept is successfully employed in the virtual reality environment byusing electromagnetic fields and forces in three dimensions. Theelectromagnetic fields generate the force feeling on the human operatorwithout the human operator being attached or connected to a referencesource, thereby increasing the realism of the simulation.

SUMMARY OF THE INVENTION

Multi-dimensional, non-linked method and apparatus for producing asimulated feeling of force by generating a first, constant, stationaryelectromagnetic field and a second, interacting electromagnetic fieldlocal to the human operator. The second electromagnetic field is varyingand is controlled by electrical currents which are responsive toparameters describing the location of the human operator and suchvariance results in attraction and repulsion between the first andsecond electromagnetic fields producing a non-linked magnetic fieldforce on the human subject.

An object of the present invention is, therefore, to provide a magneticfield force to a human subject.

Another object of the invention is to provide a magnetic field force toa human subject with the human subject free from any attachments orlinks to a reference frame.

Another object of the invention is to provide a feeling of force to ahuman subject for complete immersion in a virtual reality environment.

Another object of the invention is to provide a non-linked magneticfield force to a preselected location or perception point on a humansubject.

Another object of the invention is to provide a multi-dimensionalmagnetic field force to a human subject free from any attachments to areference frame.

Another object of the invention is to provide a multi-dimensionalnon-linked magnetic field force to a preselected location on a humansubject for complete immersion in a virtual reality environment.

Additional objects and features of the invention will be understood fromthe following description and the accompanying drawings.

These and other objects of the invention are achieved by a non-linkedmethod for providing a feeling of force to a human operator comprisingthe steps of:

generating a first, constant, stationary electromagnetic field;

sensing position and three-dimensional orientation of said humanoperator relative to said first, constant, stationary electromagneticfield;

producing a second, varying electromagnetic field local to said humanoperator responsive to position and three-dimensional orientation ofsaid human operator;

directing a force on said human operator resulting from attracting andrepulsing forces between said first and second electromagnetic fields.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a stator and rotor arrangement used ina DC motor in the prior art.

FIG. 2 is a frontal view of a glove type untethered virtual realityforce emulator apparatus in accordance with the invention.

FIG. 3 is a schematic diagram showing force developed on a conductor inan electromagnetic field.

FIG. 4 is a schematic of an actuator element.

FIG. 5 is a glove type apparatus immersed in an electromagnetic field inaccordance with the invention.

FIG. 6 is a schematic of a layered actuator element.

FIG. 7 is a diagram showing the geometry of force vectors.

FIG. 8 is a shoulder-to-arm force emulator system in accordance with theinvention.

FIG. 8a is a diagram showing references for angular displacement inaccordance with the invention.

FIG. 9 is a diagram showing a solenoid with an associatedelectromagnetic field.

FIG. 10 shows a Helmholz coil generated magnetic field in accordancewith the invention.

FIG. 11 shows Helmholz coil generated magnetic fields in two planes.

DETAILED DESCRIPTION

The invention may be better understood by first considering the basicconcepts of electromagnetic interaction and force generation, as isemployed in a DC motor, for example, and then extrapolating suchconcepts to the present invention. FIG. 1 shows a prior art DC motorthat is known in the art. In FIG. 1, the stationary part of the motor,or the stator, is shown to include the magnetic poles at 100, 101, 102and 103. The rotating part of the motor, or the rotor, is shown at 104.The mechanical load rotated by the motor is shown at 108. The statorpoles, 100, 101, 102 and 103 remain stationary and have constantmagnetic polarities associated with each of them, polarities controlledvia external power excitation as indicated at 109. The magnetic field atpoles 100 and 102 have a North magnetic polarity and the magnetic fieldat poles 101 and 103 have a South magnetic polarity. The lines of fluxthat become generated by these opposite magnetic polarities areindicated at 110.

The rotor, indicated in FIG. 1 at the center of the motor diagram by thebarbell type device at 104, has a North magnetic pole shown at 105 and aSouth magnetic pole shown at 106. It is generally known in the area ofelectromagnetics that the South pole 106 is attracted to the North pole102 and conversely. Also, if a North pole encounters another North pole,the two poles repel. This repulsion also occurs if a South poleencounters a South pole. In the instant shown in FIG. 1, the rotor 104at the pole 105 is therefore being repelled by the stator at pole 100and simultaneously being attracted to stator pole 101. This tends toproduce rotation in a counter-clockwise direction. When the rotor pole105 arrives at the stator pole 101, the currents in the rotor winding,shown at 111 are changed such that the polarity of pole 105 is changedfrom North to South. Since the rotor 104 was already moving, theadditional repulsion between poles 101 and 105 will now move the rotorfurther in a counterclockwise motion towards stator pole 102. Recallstator pole 102 has a North polarity and pole 105 of the rotor (now witha South polarity) will then be attracted to stator pole 102. This motioncontinues with the polarity of the rotor poles changing every quartercycle as the rotor moves in the counter clockwise manner shown at 107.

The rotor 104 is often attached to a load, a load generally depicted at108 in FIG. 1, thereby the initial electrical energy input to the motordevice is transformed into mechanical energy of load rotation. Thedevice thus described is one-dimensional and functions in a planar typeof movement. The DC motor of FIG. 1, therefore, may be considered todemonstrate the concept of “action at a distance”, a method of forcegeneration in which mechanical energy is transferred to the environmentwithout any objects or surfaces coming into direct contact with oneanother. This is different from the traditional Newton's Third Law“action-reaction” scenario in which an object reacts to a given forcethrough direct contact.

To better understand what other variables may influence the forcegenerated via electromagnetic interaction, and hence better understandthe invention, it is worthwhile to examine how a force can be producedon a single electrical particle by its movement in an electromagneticfield. From the basic principles of physics, the force acting on acharge q, when moving with a velocity v in an external field, can bedescribed by the relationship:

F=q v×B   (Eq. 1)

Where the vector v is a velocity vector indicating the direction of thecharge q relative to the external (constant) B field. The variable B isthe magnetic induction vector that has units of Webers/meter². The crossproduct term x indicates that the force acting on the charge q is atright angles to both the v and B vectors. Thus, the force generated isproportional to the quantity of charge, its velocity, the intensity ofthe external B field, and the orientation between v the vector and the Bfield. To illustrate this basic principle of physics, consider FIG. 3,which illustrates the relationship of Eq. 1 for the flow of many chargesq. FIG. 3 shows a magnetic field B at 303, current at 301 and conductorlength at 302. In FIG. 3, the flux lines of the B field are shown at300, a current is shown at 301 moving from right to left in a conductorwhose length is illustrated at 302. The current i(t), shown at 301, is asummation of charges and the force, F, on the conductor can be expressedby the relationship

F=i(t) L×B   (Eq. 2)

Where L is a vector indicating the direction of the current i(t). Eq. 2is similar to Eq. 1 but applies for multiple charges and demonstratesthe dependency of the force developed on the quantity and orientation ofthe current as well as the length of the conductor L affected in theexternal B field. The principle of the operation of a force generated ona conductor as depicted in FIG. 3 provides a basis for all types offorce generation in electromagnetic devices including electric motors asshown in FIG. 1. The effect could also be illustrated through theinteraction of two electromagnetic fields, that is, the external fieldhaving flux lines at 300 in FIG. 3 and a field generated by the currentshown at 301 in FIG. 3 opposing the external field at 300. This is thebasis of force generation for the non-linked magnetic field force systemof the invention.

This effect may be extrapolated to an arrangement of the inventioninvolving a glove device in a virtual reality simulation as shown inFIG. 2 where the external magnetic field shown at 200, and the glovedevice generally shown at 202 operates in a magnetic field. Forceactuators are shown at 204. An attached microprocessor, such as is shownconnected at 203 in FIG. 2, is responsible for computing the actualposition and orientation of the body part, a hand in the arrangement ofFIG. 2, to institute necessary currents in the force actuators.Referring to the description of the DC motor, the external field 200remains constant as do the stator poles at 100, 101, 102 and 103 in FIG.1. The rotor, at 104 in FIG. 1, has a current coil therein whose currentvalued is changed, this in turn changes the polarity of the rotor poles.A similar action occurs in the force actuators 204 on the glove devicein the arrangement of FIG. 2. The current within the force actuatorchanges value, which in turn changes the magnetic field local to theglove device. Assume for example, that a feeling of force is desired onthe glove-type device, the actual orientation of the glove-type deviceis determined by the microprocessor, which obtains position andorientation information in the form of electrical signals from thegoiniometers at 205. After data indicating the three-dimensionalposition and orientation of the glove-type device with respect to themagnetic field 200 are communicated to the microprocessor, themicroprocessor then computes the value and vector direction of themagnetic field local to the glove-type device needed to cause the staticelectromagnetic field to repulse the local magnetic field and emulate afeeling of force in the intended direction on the glove-type device. Asample software algorithm is provided as Appendix A, which providesmeans for the microprocessor to coordinate and keep track of positionand orientation of the sensors and actuators. The software algorithm iswritten in MS BASIC language.

The FIG. 10 arrangement of the invention uses a Helmholz type coil togenerate a first, constant, stationary magnetic field. The Helmholzcoils are shown at 1010 in FIG. 10 and the glove-type device is shown at1020. The Helmholz coil is known in the art and has the unique abilityto produce an electromagnetic field which is very uniform andhomogeneous. The flux lines of the magnetic field generated by theHelmholz coil are shown at 1040. After the electromagnetic field 1040 ismaintained constant, the glove-type device 1020 is then inserted intothe field, the glove-type device appended with a three-dimensional forceactuator shown at 1030. In relation to the DC motor example, theHehmholz coil acts as a stator and the three dimensional force actuator1030 equates to the rotor device.

Another possible arrangement for generating a more than one constant,stationary electromagnetic field is by using two Helmhotz coil generatedmagnetic fields at right angles to each other as shown in FIG. 11. Suchan arrangement allows for non-linked magnetic field force generation inmore than one plane. In FIG. 11, a first constant electromagnetic fieldis generated between Helmhotz coils shown at 1111 and 1112 with theassociated magnetic flux lines flowing in the “X” direction on the worldcoordinate system. A second electromagnetic field, perpendicular to thefirst electromagnetic field is generated between Helmhotz coils shown at1113 and 1114 with the associated magnetic flux lines flowing in the “Y”direction on the world coordinate system. If the magnetic fields of FIG.11 are pulsed on and off sequentially every millisecond, it is possibleto generate non-linked magnetic field forces in more than one plane on,for example, a glove-type device inserted within the magnetic fields, ina similar manner as force generation accomplished in a single plane.

There are various ways to determine the actual orientation of the humansubject's body part, the hand in the arrangement of FIG. 2 that willreceive a virtual reality force. The determination is not entirelydifferent from having a global positioning system at each key joint ofthe human operator to determine the position and orientation of eachrespective coordinate frame in space. One method of determining positionand orientation, commonly accomplished in the field of robotics is bymeasuring the changes of the joint angles and the lengths of therespective links making up the system. In FIG. 8, a shoulder-to-armarrangement of the invention is depicted. The flux lines of the first,stationary, constant magnetic field are shown at 800, the forceactuators are shown at 801 and goiniometers or position and orientationsensors are shown at 802 and 803. Simple trigonometric measurements ofthe arm system using goiniometeres 802 and 803 as shown in FIG. 8 areused to determine the joint angles.

FIG. 8a is a diagram of the angle relationships of the position sensors802 and 803 in FIG. 8. The goiniometer has a fixed reference base asindicated at 805 in FIG. 8a and is the origin of the world coordinatesystem. The angles shown at 806 and 807 are each sensed via either arotational potentiometer or an encoder, which counts the number ofpassing slots as the angle 806 changes. For example, a 10-bit encoderhas 2¹⁰=1024 slots and for a full rotation of 360 degrees, the degreechange per slot is 360 degrees divided by 1024 which equals 0.352degrees per slot. Thus, the angle: 806 and 807 in FIG. 8a can be sensedas they change. Similarly, the lengths shown, at 810 and 811 are alsoknown as shown in the algorithm of the microprocessor, attached asAppendix A. Thus in FIG. 8a, the point shown at 809 can be y-axislocated with respect to the origin at point 805 by the lengthrepresented at 810 multiplied by the sine of angle 806 and adding theproduct of the length represented at 811 multiplied by the sine of angle807. Similarly, the x-axis position change of point 809 relative to theorigin at point 805 can be determined by multiplying the lengthrepresented at 810 by the cosine of the angle at 806 and adding theproduct of the length represented at 811 by the cosine of the angle at807. Therefore, the microprocessor contains an algorithm to locate thepoint at 809 representing the human subject's body part, relative to theorigin at point 805, utilizing only the lengths represented at 810 and811 and the measurement of angles 806 and 807. The joint angles can besensed by devices other than goiniometers and the art has demonstratedalternative means such as potentiometers and magnetic devices forachieving this objective.

Knowing the location of point 809 in FIG. 8a, or the human subject'sbody part, relative to the origin at 805 allows the microprocessor tothen generate a current in the windings of the force actuators, which inturn produces, a proportionately valued electromagnetic field. Anelectromagnetic field of appropriate polarity local to the human subjectand having a lower strength than the static, stationary electromagneticB field will result in the B field repulsing the field local to thehuman subject resulting in a feeling of force on the human subject. Thefield B at 800 in FIG. 8 is constant, however, the local field at 801may vary with time, producing a force reflected on the human, whichvaries with time. The variation of the forces produced at 801 willchange depending on the position and orientation of the human arm. Itis, therefore, the operation of the microprocessor to track theorientation of the force actuators as well as to coordinate theirrelative movement. The microprocessor will allow the gradual changes inforces such that the human operator does not experience sudden or abruptforce changes.

The inputs and outputs required for the microprocessor to work includeall joint lengths and prior knowledge of the link lengths. As shown inFIG. 8a, each position sensor has a reference point and the goal is totrack the position of the most distal point, point 809 in FIG. 8a. Onemethod for accomplishing this task is to use the Denavit-Hartenberg(hereinafter “D-H”) method. The D-H method involves using a matrix,which keeps track of both position, and orientation changes as the humansubject moves and rotates through space. The D-H matrix is of the form$\begin{matrix}{{\,_{\,^{A}B}T} = \begin{bmatrix}R & P \\{0,0,0} & 1\end{bmatrix}} & \text{Eq.~~4}\end{matrix}$

where R is a 3×3-rotation matrix, and P is a 3×1 column vector whichtracks the change in position. The 4×4 matrix ^(A) _(B)T tracks thechange in position when the system moves from frame A to frame B.Appendix A illustrates representative software in MS BASIC to show asimple example in implementation.

FIG. 5 illustrates how both position and orientation can be trackedusing a D-H matrix. A system is originally in frame A, shown at 500 andidentified at 501 in FIG. 5, and is rotated and translated to frame B at506 and identified at 507 by a 30 degree rotation, such angle shown at502, about the Z axis of frame A and translated 4 units in the X_(A),503, direction and 3 units in the Y_(A) 504, direction. The D-H matrixcorresponding to FIG. 5 is $\begin{matrix}{{\,_{\,^{B}A}T} = \begin{bmatrix}{A_{B}R^{T}} & {{- {{}_{}^{}{}_{}^{}}}{{}_{\quad}^{}{}_{}^{\quad}}} \\{0,0,0} & 1\end{bmatrix}} & \text{Eq.~~5} \\{{{where}\quad {{}_{\,^{A}B}^{}{}_{}^{}}} = \begin{bmatrix}{c\quad \theta_{z}} & {s\quad \theta_{z}} & 0 \\{{- s}\quad \theta_{z}} & {c\quad \theta_{z}} & 0 \\0 & 0 & 1\end{bmatrix}} & \text{Eq.~~6}\end{matrix}$

where cθ_(z) and sθ_(z) are short hand notation for cosine and sine ofthe angle θ_(z). The vector ^(A)P_(BORG) is given by col[4,3,0] and$\begin{matrix}{{\,_{\,^{B}A}T} = \begin{bmatrix}0.866 & 0.5 & 0 & {- 4.964} \\{- 0.5} & 0.866 & 0 & {- 0.598} \\0 & 0 & 1 & 0 \\0 & 0 & 0 & 1\end{bmatrix}} & \text{Eq.~~7}\end{matrix}$

The result shown in Eq. 7 is called forward kinematics. To determineinverse kinematics, compute ^(A) _(B)T by inverting the matrix of Eq. 7.In practice, the angles θ are measured, the rotation matrix is known,the P_(BORG) matrix is determined using the known link lengths and ^(A)_(B)T or ^(B) _(A)T is calculated.

Thus, the D-H matrix keeps track of both the position and orientationchange of a coordinate frame and can be used to track the point 809 inFIG. 8a, as an example. It is only required to know the link lengths andthe angle changes to determine both the position and orientation ofpoint 809.

To calculate the strength and size of the magnetic fields used in theinvention, the first, constant, stationary magnetic field and thevarying magnetic field local to the body part of the human subject,assume, as an example, a 0.2 pound force is desired. Studies in the artdealing with subjects involving force-reflecting devices generally havedemonstrated that significantly less than one pound of force on the armor hand over any period of time exceeding a few seconds is extremelyinstrumental in modifying limb motion trajectories. It is easier toconsider this problem in SI (Systems International) units. Thus, 0.2pounds of force =0.2/(0.2248 pounds/Newton) which is approximatelyequivalent to 1 Newton of Force.

The equation B=u_(o)i_(o)n may be used to determine the parameters of asolenoid capable of providing an external magnetic field B supportingthis force of 1 Newton. FIG. 9 shows a typical solenoid with an externalelectromagnetic field where n is the number of turns 901 of wire on thesolenoid shown at 903, i is the current in the solenoid as shown at 902,and u is the permeability of air =4π×10⁻⁷. Thus, as an example, asolenoid of 1 meter in length, 3 centimeters in diameter, which has 10layers of windings of 850 turns each and carries a current of 10 amperesgenerates an external field of 0.11 Weber/meters². Note that a Weber is10⁸ lines of force per square meter and levels of 0.1 Telsa(Webers/meters²) is not considered hazardous by OSHA standards. Afterthe external field B is established, the force can be determined thatacts on the actuator via the relationship set forth in Eq. 2.

The unattached force emulating device and method of the invention may beaccomplished in three dimensions, increasing the realism of thesimulation. FIG. 4 illustrates a three-axis element for use in athree-dimensional force reflection paradigm. A three-axis coil elementwhich can generate forces and moments in all three-dimensions isobtained by wrapping three coils, shown at 400, 401 and 402 in FIG. 4,about three ferrous metal cores shown at 403, 404 and 405 in orthogonalaxis.

The three ferrous metal cores 403, 404 and 405 only touch each other atthe X, Y and Z-axes, shown at 406, 407 and 408, respectively. At theintersections of the X, Y and Z-axes at 406, 407 and 408, the threeferrous metal cores are isolated from one another by a varnishingseparator which provides high electrical resistance to eddy currentsthat may be induced yet permits the magnetic fields to be focused andconcentrated in the ferrous material composing each ferrous metal coreof the respective axis. Since each coil wrapping, 400, 401 and 402 isorthogonal to the other two axes, this provides independent control. Thewires carrying the control current from the microprocessor to each ofthe orthogonal coils have currents i_(x), i_(y) and i_(z) which giverise to their respective electromagnetic fields. One, two or three ofthe axes may be actuated simultaneously. It is not necessary to actuateevery axes, only those necessary for creating the appropriate forcevector. Accordingly, if a three-dimensional feeling of force is desiredon the human operator, a microprocessor will be programmed to alter thecurrents 400, 401 and 402 and a feeling of force will be emulatedagainst the electromagnetic fields local to each current. Such athree-dimensional force emulation is more realistic than force emulationin a single plane.

The actuating elements which produce the force locally on the glovedevice in FIG. 2 have the design in FIG. 4 for another reason involvingthe removal of heat in an efficient manner. Heat is removed in anefficient manner because heat generating electric currents have to runthrough the coils 400, 401 and 402 in order to generate theelectromagnetic field and a feeling of force. The design in FIG. 4reduces heat in an efficient manner by having each axes exposed to theair and separated in a spatial sense. This design allows for betterconduction of heat from the device.

The three-dimensional force reflecting actuators can be furthersimplified as illustrated in FIG. 6. FIG. 6 shows a force actuator, 600with two metal cores 601 and 602 on top of each other and at a rightangle to metal core 603. In FIG. 6, the three-axis coil, 600, is put ina form that appears as a two-dimensional plane but effectively acts aslike a three-dimensional actuator (as in FIG. 4). In FIG. 6, actuatorbottom layers 601 and 602 are produced from material anisotropic innature, that is, the magnetic properties of the material are morefavored in one direction only as compared to isotropic materials inwhich magnetic properties are similar in all directions simultaneously.These properties of magnetic substances can be built into the materialas the metal is formed and provides the directional vectors without theneed for three-dimensional construction as depicted in FIG. 4.

This arrangement can be further understood by considering FIG. 7. FIG. 7illustrates the three force vectors that result when actuated by theseorthogonal electrical currents from the system in FIG. 4. From FIG. 7,in the x, y and z directions shown at 700, 701 and 702, respectively, itis known these vectors now have forces in their respective coordinatesystems through the vector relationship

F_(j)=i_(j)L×B   Eq. 3

Where the currents j=X,Y, or Z have been initiated by a microprocessorto the respective coils. By combining any two or more forces using Eq.3, it is seen from FIG. 7 that force reflection can easily beaccomplished in any arbitrary direction. A difficult task is for themicroprocessor to keep track of the position and orientation of theforce actuators on the human subject, a glove-type device in FIG. 2, andto coordinate their relative movement. With this information on thehuman subject, the hand in the arrangement of FIG. 2, the appropriatecurrents i_(x), i_(y), and/or i_(z) can be generated to command theappropriate spatial force reflection paradigm.

The invention provides a more realistic feeling of force simulation thanthat available in the art by capitalizing on the concept of an “actionat a distance” method of reflecting forces as opposed to the traditionalNewton's third law concept of “action-reaction” with bodies in contact.The “action at a distance” concept is successfully employed by usingelectromagnetic fields and forces in three dimensions without the humanoperator being attached or linked to a reference source.

While the apparatus and method described herein constitute a preferredembodiment of the invention, it is to be understood that the inventionis not limited to this precise form of apparatus or method, and thatchanges may be made herein without departing from the scope of theinvention, which is defined in the appended claims.

We claim:
 1. A non-linked method for providing a feeling of force to ahuman operator comprising the steps of: generating a first, constant,stationary electromagnetic field; sensing three-dimensional position andorientation of said human operator relative to said first, constant,stationary electromagnetic field; communicating data from said sensingstep to a microprocessing computing device; generating an electricsignal responsive to data from said communicating step; producing asecond, varying electromagnetic field local to said human operatorresponsive to said electrical signal from said generating step; andcoupling a force generated by interaction of said first and secondelectromagnetic fields to said human operator.
 2. The method of claim 1for providing a feeling of force to a human operator wherein saidgenerating step further includes the step of providing a helmhotz-coilgenerated electromagnetic field.
 3. The method of claim 1 for providinga feeling of force to a human operator wherein said sensing step furtherincludes the steps of: establishing a coordinate system relative to saidhuman subject; and sensing movement of said human subject by measuringangular and linear displacement of said human subject relative to saidcoordinate system.
 4. The method of claim 1 for providing a feeling offorce to a human operator further including the step of generating anelectric signal in each of x, y and z coordinate axes.
 5. The method ofclaim 3 for providing a feeling of force to a human operator, whereinsaid sensing step further includes the steps of: mounting said humanoperator with position sensing equipment; and mounting said humanoperator with force actuating equipment.
 6. The method of claim 4 forproviding a feeling of force to a human operator, wherein said mountingsaid human operator with position sensing equipment further includes thestep of mounting said sensing equipment on a glove type device on a handof said human operator.
 7. An non-linked system for providing a feelingof force to a human operator comprising: a first, constant, stationaryelectromagnetic field generating apparatus; sensing apparatus appendedto said human operator for locating three-dimensional orientation ofsaid human operator relative to said first, constant, stationaryelectromagnetic field; a second electromagnetic field local to saidhuman operator and responsive to three-dimensional position andorientation data of said human operator; a computer apparatus capable ofvarying said second electromagnetic field to generate attractive andrepulsive forces acting on said human operator in response to signalsreceived from said sensing apparatus.
 8. The system of claim 7 forproviding a feeling of force to a human operator further including datacommunication means for communicating data from said sensing apparatusto said microprocessing computing device.
 9. The system of claim 7 forproviding a feeling of force to a human operator wherein said attractiveand repulsive forces are generated by an electric signal.
 10. The systemof claim 7 for providing a feeling of force to a human operator furtherincluding a second electromagnetic field existing on x, y and z axis ofa world coordinate system.
 11. The system of claim 10 for providing afeeling of force to a human operator wherein said second electromagneticfield of three-dimensions comprises a first metal core in the x-plane ofthe world coordinate system having current carrying coils thereon; asecond metal core in the y-plane of the world coordinate systemorthogonal to said first metal core having current carrying coilsthereon; a third metal core in the z-plane of the world coordinatesystem orthogonal to said first and second metal cores having currentcarrying coils thereon; and said current carrying coils of said first,second and third metal cores having a current running therethrough andgenerating an associated electromagnetic field that attract and repelsaid first electromagnetic field.
 12. The system of claim 11 forproviding a feeling of force to a human operator wherein said secondelectromagnetic field of three dimensions comprises a first core ofanisotropic material in the x-plane of the world coordinate systemhaving current carrying coils thereon; a second core of anisotropicmaterial in the x-plane of the world coordinate system having currentcarrying coils thereon; a third metal core in orthogonal to said firstand second metal cores having current carrying coils thereon; and saidcurrent carrying coils of said first, second and third metal coreshaving a current running therethrough and generating an associatedelectromagnetic field that attract and repel said first electromagneticfield.
 13. The system of claim 7 for providing a feeling of force to ahuman operator wherein said sensing apparatus further comprises: meansfor establishing a coordinate system relative to said human subject; andsensing means for sensing movement of said human subject by measuringangular and linear displacement of said human subject relative to saidcoordinate system.
 14. The system of claim 13 for providing a feeling offorce to a human operator wherein said sensing means further includes:goiniometers for sensing position of said human subject; and forceactuators for sensing three -dimensional orientation of said humansubject.
 15. The system of claim 13 for providing a feeling of force toa human operator wherein said sensing means further includes aglove-type device for mounting said goiniometers and force actuators onthe hand of said human operator.
 16. The system of claim 8 for providinga feeling of force to a human operator wherein said electromagneticdevices are externally powered.
 17. An untethered system for providingforce virtual reality to a human operator comprising: a first, constant,stationary electromagnetic field; externally powered sensing apparatusappended to a glove-type device on a hand of said human operator fordetermining three-dimensional angular and linear orientation of saidhand of said human operator relative to said first, constant, stationaryelectromagnetic field; a second electromagnetic field local to saidhuman operator and responsive to three-dimensional angular and linearorientation data of said hand of said human operator; a microprocessingcomputing device operative to receive and generate data to vary saidsecond electromagnetic field to generate attractive and repulsive forcesbetween said first and second electromagnetic fields which direct aforce on said human operator.